Pros: An iPod backpack that adds 20-30 hours of life to recent iPod models, compatible with 3G, 4G, mini and photo iPods. Easy to travel with, and use with or without belt clip. Does better job squeezing juice out of AA batteries than competitors.

Cons: iPod’s backlight flips on and off during discharge cycle, requiring you to turn it off; can’t revive a dead iPod, so you’ll need to start with some iPod life left; not the most stylish low-capacity battery we’ve seen; requires you to supply new AAs.

If you’re not as concerned about the style of your iPod battery pack as its cost-to-performance ratio, you’ll be impressed by the total package offered by Battery Technology Incorporated (BTI)‘s new AA iPod Battery ($49.95). As the company’s cheapest, smallest, and lowest-capacity iPod battery solution to date, the AA iPod Battery uses four AA batteries rather than a rechargeable internal power cell, and connects to any 3G, 4G, mini or photo iPod via its bottom Dock Connector port. Like its predecessors, it boosts your iPod’s run time and outperforms the company’s modest estimates by a considerable factor.

As with the company’s iPod Battery ii (iLounge rating: A-), the biggest component in this package is a white plastic battery holder with four power indicator lights on its top, a button to activate them, and an official Apple Dock Connector cable hanging from its bottom. The AA iPod Battery has an significant on-off switch on its bottom, rather than the almost invisible one on its predecessor’s side, and no power adapter or port on its casing to recharge the batteries inside. In other words, if you want to use rechargeable AA cells, you’ll need to use a separate battery recharger.

The AA iPod Battery’s battery compartment has changed in a few other ways, too. It’s shorter - under 3 3/8 inches (.75 inches smaller than the iPod Battery ii) - and slightly less wide as well, measuring under 2 3/4 inches. Thickness has increased only a little to 11/16 of an inch to accommodate the four AAs. Consequently, the pack looks less obtrusive than its predecessors, and fits better alongside an iPod than ezGear’s PowerStick, for example. But it’s still in no way as svelte or contoured as the most recent rechargeable offerings from Nyko (iBoost) or Belkin (TunePower).

Overall, it is best compared in size and profile with Belkin’s older but more sleek Backup Battery Pack (iLounge rating: B). Belkin’s Pack carries a current MSRP of about $10 more, but can be had for less if you shop around. However, unlike Belkin’s product, which works only with full-sized iPods, BTI’s AA iPod Battery also works with iPod minis thanks to a set of three included plastic iPod clips - one each for mini, thin, and thick iPods.

The holder’s front panel pops off to reveal a compartment with spots for each of the four AA batteries. Once they’ve been inserted, you replace the front panel, which loosely grips the pack until one of the three iPod clips is attached; at that point the whole unit becomes physically stable and significant feeling. A sturdy spring-loaded belt clip may be attached to the unit’s rear; or left off for non-belt carrying. Once you’ve inserted your iPod into one of the clips, you connect the Dock Connector plug and switch the power on.

We haven’t been totally thrilled by the clips on the previous iPod Batteries - they’re not super-protective, and don’t let you attach an already-encased iPod. The new clips are just like those on The iPod Battery ii - so-so. Each fit our test iPods, though they varied in tightness a bit from unit to unit - they were never too loose, but sometimes felt pretty tight. As better battery pack mounting solutions have appeared in recent months (the softer plastic in Belkin’s TunePower as just one example), we’ve become less enamored with this particular plastic clipping solution; whether you’ll mind its limitations will depend on how you use your iPod when attached to the battery. If you’re planning to make use of it in the safety of airplanes or someplace else where your iPod won’t be scratched, you’ll be fine, but just don’t expect to use it on the go.

Additionally, as was the case with The iPod Battery ii, you can detach the iPod and belt clips from the AA iPod Battery’s pack and connect them to each other instead. This gives you an inexpensive and not especially protective way to carry your iPod, but it’s a feature of the product nonetheless, so we note it.

The single best feature of the prior iPod Batteries was the extra play time they delivered: in each case, they outperformed BTI’s promised numbers by a staggering amount, delivering literally multiple days of continuous play time off a single charge. BTI’s claimed play time extension for the new battery is a real lowball - 10 hours - that you’re unlikely to see unless you’re using terrible batteries and an 3G iPod with its screen on for excessive periods of time. In fact, we found that the AA iPod Battery delivered two or three times that number under our typical test conditions with recent iPods: randomized playback, equalizers off, volume on 50% with earbuds attached.
There were a couple of wrinkles, though, that impact the accuracy of any performance testing that can be done on the AA iPod Battery. First, since there’s no “standard” AA battery out there for testing purposes, we went with a fresh set of standard Energizers. Better or worse batteries may well vary from our numbers. Second, when we started with a fully-drained iPod and tried our tests - our standard procedure - the AA iPod Battery wouldn’t work. Consequently, we had to recharge our iPods for the tests and subtract their estimated run times from the total numbers we saw after our tests.

But the numbers were good - in fact, very good by comparison with competing AA products such as Belkin’s Backup Battery Pack. Our test first-generation iPod mini ran for a total of 32 hours, 25 minutes with the AA iPod Battery attached, which means that it added around 22 hours of additional run time to the iPod’s own charge. Our fourth-generation iPod ran for 42 hours and 45 minutes with the battery attached, suggesting that the Battery added around 30 hours of additional run time to the iPod’s own battery. Owners of iPod photos and second-generation minis can expect to see even greater play time extensions.
So the new AA iPod Battery’s positives - extended play time and full iPod/iPod mini mounting and belt-clipping compatibility - are fairly obvious. We did have a couple issues with the product, however, that may or may not be of great importance to typical users. As with BTI’s prior iPod Batteries, we found that the remaining power indicators were inconsistently useful; they worked better in our test of the 4G iPod, but with the iPod mini repeatedly flipped between two lights, one light, and zero lights in the second half of the Battery’s life. We’ve seen somewhat similar things happen with other companies’ iPod batteries, especially ones based on AA power, so we’re not seriously concerned about this, but think that an indicator scheme other than four lights would be better than one that always seems to be telling you something different.

We had more serious concerns about a weird little issue that started at the tail end of the Battery’s useful life with our iPod mini, and in the middle of the life cycle of our 4G iPod: the iPod’s backlight began to flip on and off repeatedly as the batteries drained until we turned off the light altogether. This is just a guess, but we think that the initial screen illumination may have been the iPod’s attempt to signal that it was no longer using the power from the Dock Connector port, and that it flipped on and off whenever there was enough AA juice to confuse the iPod into making a connection. Regardless, it was odd to watch, and probably not great for the iPod’s lamp - a fairly major factor in our final rating of the product. Therefore, we would only recommend you use your iPod normally (with backlight settings unchanged) with the iPod Battery to its promised 10-hour point, and suggest you turn the backlight off entirely after that.
Overall, BTI’s AA iPod Battery generally lives up to the strong power performance standards of its predecessors, delivering tens of hours of additional iPod playback on the same four AA cells that other companies have mined for far less impressive results. While its performance will vary based on the batteries and iPod you’re using, you can expect that it will outlast other AA-based iPod battery solutions attached to the same power and power-draining sources, as well as comparably rated (and frequently more expensive) thin battery packs for the iPod. That’s its strongest selling point against all competitors; its inclusion of iPod and belt clips is another advantage against cheaper competitors such as ezGear’s PowerStick.

You’ll only have to compromise in three ways: iPod power maintenance - in other words, not draining the iPod’s internal battery to zero - normal use of your backlight, and style. The first two of those reasons - primarily the second - compelled us to knock the Battery’s overall rating down from the A- it otherwise would have received, and place it on par overall with similar AA-based products. However, if you can ignore these factors, you’ll prefer its ability to maximize the value you get from a single set of AA’s, and will like that it will cost you less over time in battery purchases. It’s a recommended product - just for specific users who can live with or work around its quirks.

Jeremy Horwitz is Editor-in-Chief of iLounge.

Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
This iLounge article provides more information on this practice, known as revving.